It is useful to know certain characteristics of a borehole for drilling operations. During the lifespan of an oil reservoir, samples of production fluid from the reservoir can be collected and analyzed. In order to effectively sample the production fluid from a subsea well, sampling systems are often located subsea, in close proximity to the wellhead. Wellhead sampling presents a challenge due to the potential for dispersed and mist flow from the wellhead containing both liquid and gas phases (multiphase flow). In order to properly sample multiphase flows the liquid phase must be separated from the gas phase. Multiphase flows exhibiting a dispersed or mist flow regime can be difficult to separate into component liquid and gas phase flows, in turn making the collection of liquid-only samples more difficult.
Conventional sample systems use a flow device, such as a venturi or an orifice plate, to generate a pressure differential that is proportional to the production flow. However, if the production flow rate is too low, the pressure differential generated by the flow device may be insufficient to retain a sample that contains both liquid and gas. Further, for a 2-phase flow (gas-liquid), a high pressure differential is needed to retain a liquid sample. This is due to a high level of turbulence/velocity being required to keep the liquid in a gas suspension.